Air-inlet scoop for carburetors



March 5, 1946. E. s. ECKEL 2,395,997

AIR-INLET SCOOP FOR CARBURETORS Filed Feb. 4, 1943 IN VEN TOR.

Patented Mar. I 5, 1946 UNITED STATES PATENT OFFICE- AIR-INLET SCOOP FOR CARBURETORS Earle S. Eckel, Washington, N. J., assignor to Ralph L. Skinner, Detroit, Mich.

Application February 4, 1943, Serial No. 474,680

2 Claims. (01. 261-14) This invention pertains to certain features of betterment and superiority in the so-called scoops for the admission of air to the intake of the carburetor of the internal-combustion engine of an airplane, such scoops being ordinarily located directly back of the propeller of the aircraft.

The present construction'of such scoops is defective and deficient both as to structural and functional properties and the aim of the current invention is to provide an improved construction which satisfactorily overcomes and avoids such inefficient characteristics of the present-day scoops.

These structures are designed to feed cold-air or hot-air, or a combination of the two, to the air-inlet of the carburetor associated with the engine of the airplane, and, in order that they may perform their functions under the various conditions under which the airplane operates, it is important that they have certain adequate and valuable operative attributes or capacities in which scoops of the present day style are more or less lacking.

One improved feature of the new scoop is the location of a butterfly-valve controlling the cool and heated air, pivoted close to the center of the scoop housing instead of near the bottom of the structure as is now common practice.

This valve is pivoted or hinged slightly offcenter on the so-called ram or pressure-side, whereby the valve remains stationary under normal operation without aid of ratchet or holding or retaining means. I

Such slightly-unbalanced valve permits the full flow of either hot or cold air, or a mixture of both if desired, to the carburetor, and when such a mixture is employed, this is accomplished inside of the scoop instead of directly below the venturi as is commonly done and which is not a good procedure.

In the known type of scoop, the valve is hinged at the bottom of the scoop-housing, and, with such a structure, a change from hot-air to coldair, or vice versa, causes an undesirable momentary stoppage or reduction of allair to the carburetor, and, when the valve is in a neutral position, a great turbulence of air in the scoop is produced, preventing good and eflicient carburetion. In the new valve, these objectionable characteristics are avoided.

Again, in the scoop embodying this present in- .vention, when the valve is set for cold-air operation, a suitable outlet-pipe permits all hot-air to pass off into the atmosphere, thus precluding any harm to the hot-air stove which heats the air, hence lengthening the periods oi. time necessary for inspections of such stove.

Further, when a mixture of both hot and cold air is used, the same discharge or outlet pipe prevents turbulence inside the scoop, good carburetion depending upon a smooth or steady flow of air at practically zero pressure directly below the venturi.

Moreover, in the improved scoop, the one-piece construction provides greater structural strength, the central pivoted valve and its bearings and collars assures stifier side-walls, the relativelydeep scoop means less restriction to air-flow than in other types, the bottom Outlet-pipe is so located that it will discharge any excess fuel caused by pumping of the throttle, when the airplane is on the ground or floor in tail-down position no fuel can collect in the back portion of the scoop due to the fact that the butterfly-valve does not entirely close the, outlet or drain-pipe, all bolts and nuts for securing the scoop to the carburetor are on the outside of the scoop body, spot-welding which is employed affords stiffness and strength, and the extra large outlet-pipe prevents distortion of the scoop in case of back-fire.

To enable those acquainted with this art to fully understand the invention and its various advantages, a present preferred embodiment thereof has been illustrated in the accompanying drawing to which reference should be had in connection with the following detailed description,

- and, for convenience, like reference numerals have been employed to designate the same parts throughout the several views.

In this drawing- Figure 1 is a perspective view of the and its associated filter;

Figure 2 is a perspective view of the valve inside of the scoop;

Figure 3 is a vertical section through the scoop on an enlarged scale on line 3-3 of Figure 1; and

Figure 4 is a view similar to that of Figure 3 showing the valve in different positions in full and dotted lines.

In Figure 1, the scoop, as a whole, is designated I I and its companion, rectangular air-filter, through which the air enters the front of the scoop, has been denoted by the reference numeral i2, such filter being of any suitable type, the one illustrated comprising a sheet-metal cabinet or casing l3 housing a filter-medium M, the other. wise open front of the casing being covered with a wire-mesh member I5 through which the air new scoop readily flows, the back of the filter being open,

with the filter mounted in any approved manner 'in front of the converging mouth 16 of the scoop, all as is clearly portrayed, such entrance l8 leading directly into the main rectangular part [1 of the scoop, the'back of which is closed b the curved wall I8. 1

This scoop, which includes also a top wall is and a bottom wall 2| is desirably made of a single, suitably-shaped blank of sheet-metal folded to the form indicated with the joints welded together and in some cases overlapped (not shown) where permissible.

Top wall I9 is centrally apertured with the 2 opening directly connected to the flanged outlet 22 for connection to the carburetor, not shown, the flange having holes 23 for the accommodation of attachment bolts, not shown.

At its rear, the bottom-wall 2! has a dischargeopening 24 communicating with a downwardlydirected exhaust or discharge conduit 25 connecting with the external atmosphere.

One side-wall of the scoop, near its rear and at about one-half of the height of the scoop, has a hot-air inlet directly connecting with a heatedair admission conduit 26 whose flange 21 is spotwelded, or otherwise fastened, to such wall of the casing, this conduit being joined by means not shown to an air-heater or hot-air stove associated with the exhaust-pipe of the internal-combustion-engine whose carburetor derives its hot air from the scoop. I

Directly beneath the center of the outlet 22, ahead of the hot-air inlet 26, and above the front of part 25, is located the shaft 28 of arectangular butterfly-valve 29, such shaft extending through registered apertures in the two side-walls of the casing and oscillatory in a pair of exterior bearings 3| whose bases 32 are welded to the outside faces of such side-walls, the shaft at one end having an external operating arm 33 whose hub 34 on the shaft is secured thereto, the opposite protruding end of the shaft being equipped with a collar 35 flxed to the shaft, such hub and collar preventing the walls of the scoop from bulging and the bases of the bearings also stiffening such side-walls.

Referring to Figure 3, when the valve is in this position, cold-air only from the airplane propeller and/or by reason of the forward travel of the airplane is fed through the filter and scoop up to the carburetor, such air first passing through the filter and then up through the front portion only of the scoop, the valve being maintained automatically in this position by the pressure of such flowing air by reason of the fact that the lower section of the valve is slightly longer than the upper section thereof, the lower edge portion of the valve contacting with the bottom wall. of the flared mouth of the scoop and being held from further turning thereby.

Under these circumstances, all of the hot-air entering the scoop finds free and unobstructed exit therefrom to the external atmosphere downwardly through discharge-conduit 25, by reason of the fact that the air from the airplane-propeller, as indicated by the arrow I00, creates a partial vacuum in conduit 25 which draws out the heated air in the scoop, flow of any of the hotair to the carburetor being prevented by the valve which fully closes such passage.

Owing to such easy and unimpeded delivery of the hot-air, there is no danger of the hot-air stove becoming unduly heated and damaged, and,

consequently, such stove need not be inspected as often as has been heretofore essential,

when hot-air only is fed to the carburetor, as shown in the full-line position of the valve in Figure 4, such air flows directly from the hot-air inlet conduit 28 7 through the scoop above the valve to the outlet 22 to the carburetor, and the cold-air forcibly entering the front of the scoop, by reason of the travel of the airplane, passes directly below such valve into the'delivery-conduit 25, the pressure of such cold-air holding the valve in the .position shown by reason of the total greater pressure thereof on the then upper part of the valve than on the at that time lower section of the valve.

Assuming that a mixture of one-half cold-air and one-half hot-air is to be employed, the valve is turned to the middle position as presented in dotted lines in Figure 4 and the valve will be automatically maintained in such balanced position by the two equal streams of cold-air forced into the scoop, one above the longer front section of the valve and the other below such section thereof, the former flowing to the carburetor and the latter to the discharge conduit 25.

In this case, one-half of the hot-air flows above the valve to the carburetor and the other half thereof below the valve to the same outlet, it being noted that a part of the valve extends crosswise the inlet 26 dividing it more or less into two parts.

Under this condition, the pressure of the coldair forced directly into the scoop is greater than that of the hot-air from the standard type of stove into and through which external air is forced by the travel of the airplane, the pressure of such heated air being reduced by the friction imposed thereon by the walls of the elongated stove-inlet, of the stove itself, and of the conduit connecting with the scoop, whereas the pressure of the cold-air is not reduced in such amount.

Obviously, the valve may be made to take any other intermediate position to produce the desired ratio of the two streams of air and maintained or held in such relation by any approved mechanical means, such as a pawl or ratchet or the like.

It should be noted that the discharge-conduit 25 is so related to the valve and is of such size that its rear part is never closed regardless of the adjustment of the valve, and, therefore, any excess fuel due to flooding of the carburetor and draining into the scoop is immediately and automatically discharged from the scoop and this is true even when the airplane is inclined upwardly forwardly with tail down when stationary on the ground or floor, there being no trap or cavity to retain such liquid fuel in the rear section of the scoop.

An understanding of this new construction and its mode of operation under its varying conditions will afford a ready appreciation of the manner of accomplishing the originally stated aims and purposes of the invention, it being particularly worthy of attention that the location of the valve and its structure precludes undue turbulence of the air in the scoop under all conditions whereby effective operation of the carburetor is assured, that the hot-stove is properly protected against injury by the easy escape of the hot-air when needed to afford such assurance, that liquid fuel due to flooding is quickly drained away under all conditions of the scoop, etc., etc.

Those acquainted with this art will encounter no difficulty in perceiving that the invention as defined by the appended claims is not necessarily limited and restricted to the precise and exact details of structure and operation and that various changes may be resorted to within reasonable limits without departure from the heart and essence of the invention and without the sacrifice or loss of any of its material benefits and advantages.

As a supplemental feature of the invention, attention is directed to the fact that, when the airplane is coming in to land, the movable parts of the feed of the two types of air to said delivery- To meet this need, the bottom of the scoop Just to the rear of the filter is equipped with a shallow cross-wan or barrier 4| and the sloping bottom wall of the scoop just back or such barrier at each of the two corners is provided with a drain aperture 42, one of which is shown in Figure 1 and the other in Figure 3, these holes providing adequate means for quickly disposing 01' such objectionable liquid fuel.

I claim:

1. Ina forwardly-facing air-scoop for theintake of a carburetor of an airplane internal-combustion engine, including a casing having a front mouth to receive cool external-air, a hot-air inlet, an outlet at the upper portion of the casing to deliver air therein to the carburetor air-intake, a

discharge-opening at the lower portion of the casoutlet, and means to stop said valve from turning beyond its fully-open and its iully-closed cool-air positions, the novel improvement being that said valve is of the butterfly-type pivoted approximately one-half the height of said casing and at such position that when in its cool-air fully-closed position the cool-air entering the casing through its mouth has substantially-uhobstructed exit through said discharge-opening at which time the hot-air entering the casing has substantially-unobstructed exit through said delivery-outlet, and that when said valve is in its cool-air fully-open position, such air has substantially-unobstructed exit through said delivery-outlet and said hot-air has substantially-unobstructed exit through said discharge-opening.

2. The novel improvement in an air-scoop as presented in claim 1, including the additional novel improvement that the portion of said valve to the rear 01' its axis overlies said discharge-opening and when the valve is in its hot-air fully-open position it does not completely cover the rear portion of said discharge-opening, whereby liquid fuel draining from the carburetor may pass directly through the scoop and be discharged through said opening even though the'airplane carrying the scoop is in tail-down position, the back portion of the scoop being free from any cavity-capable of harboring any 01' such i'uel.

EARLE S. ECKEL. 

